Project Abstract In articulating a vision for Toxicity Testing in the 21st Century, the National Research Council (NRC) noted that exposure science will play a critical role. In this context, biomonitoring is a key component that quantitatively associates an internal dose with a measurable effect. It has also been suggested that epidemiology studies which accurately assess chemical exposures along with biological effects will have the most meaningful interpretation and thus maximal impact. A major impediment for conducting biomonitoring within epidemiology studies is the lack of rapid, field deployable, quantitative technologies that measure chemical exposures using minimally invasive biological fluids, such as saliva. Our recently completed research resulted in the development of pesticide sensor platforms, an in vivo animal model system for rapid characterization of saliva pesticide uptake and clearance, and a dosimetry model to predict systemic dose based upon a 'spot' saliva measurement. Recently, the utility of the sensor was confirmed by measuring a target analyte in saliva from pesticide manufacturing plant workers. This project has been highly successful and can be utilized as a framework for evaluating a broader range of important chemicals. Since human exposure is rarely to single agents but rather to complex mixtures, there is a need to develop biomonitoring strategies capable of measuring multiple analytes. This is particularly true in agriculture where multiple pesticides are routinely utilized on crops. Clearly there is a need to extend the strategy to other important pesticides; however, a major limitation is the inability to a priori identify which chemicals are readily cleared in saliva, hampering our ability to easily develop a multiplex screening platform. To address this challenge, it is hypothesized that chemical uptake and clearance in saliva can readily be predicted for a broad range of chemicals based upon limited in vitro experiments which are integrated into a pharmacokinetic model. To test this hypothesis this continuation project will exploit the previously developed in vivo rat model for salivary gland uptake and clearance and will develop additional in vitro cell and sub-cellular based approaches for a broad range of pesticides having differing physical and chemical characteristics as well as clearance mechanisms. Once validated, this approach can guide sensor platform development since model simulations will provide critical information on detection limits and clearance rates.